It has entered advanced information age as represented by mobile communication, cell phones, satellite broadcasting, satellite communication, CATV and the like, and the communication tends to be performed faster and higher frequency. Furthermore, according to a requirement for the miniaturization of these equipments, the miniaturization of the circuit elements also has been strongly required.
The size of a circuit element for microwave is based on the wavelength of an electromagnetic wave used. An electromagnetic wave transmitting in a dielectric material having a dielectric constant of (ε) has a wavelength (λ) represented by λ=λ0/(ε1/2) where λ0 represents the wavelength in vacuo. Therefore, since the size of the circuit becomes small in inverse proportion to square root of ε, a material having high dielectric constant has been required.
Further, relating to a display substrate such as PDP, glass for electric substrate having low alkaline content and high dielectric constant applicable for one having high density, high brightness and low electric consumption is desired. When the dielectric material is used as a capacitor in high frequency and high electric field, the material is required to have large quality constant Q. Since Q is rendered by the relational expression of Q=1/tan δ (tan δ: dielectric loss), a material having low dielectric loss is required.
Conventionally, borosilicate glass containing large amount of PbO component is known as a glass having comparatively high dielectric constant as described above. For example, SiO2—RO (R is a alkaline-earth metal) —(TiO2+ZrO2+SnO2)—PbO system glass is disclosed in Tokukaihei-3-297008A, and SiO2—PbO—Al2O3 system glass is disclosed in Tokukaihei-4-16527A and Tokukaihei-4-108631A.
It is to be noted that P2O5—B2O3—Nb2O5 system glass is known as an optical glass having high refractive index (Tokukaisho-52-132012A and Tokukaihei-8-104537A, etc.). However, the glass containing no PbO component is required in an environmental viewpoint.
However, since this glass contains large amount of alkaline, it has low resistance property to voltage because of high mobility thereof. Therefore, it is not suitable for a substrate of a high frequency circuit element and electric circuit.
The object of the present invention is to provide a material suitable as a substrate for such as a high frequency circuit element, display and the like, where the material is a glass having high dielectric constant, low dielectric loss and comparatively low alkaline content, in which the defects seen in the above-described earlier development is totally improved.